Examples of tungsten-halogen incandescent lamps having opposed press-sealed end portions are known in the art. Examples are described and illustrated in U.S. Pat. Nos. 3,392,299 (Kern), 3,443,144 (Fresse, Jr.) 3,602,761 (Kimball), 3,943,395 (Huston et al), and 4,359,665 (Morse et al), all of which are assigned to the same assignee as the instant invention. It will be understood from the following that this invention is particularly adapted to lamps of the above type which are especially suited for use in photocopiers. One particular example is shown and described in the aforementioned U.S. Pat. No. 3,943,395.
In U.S. Pat. No. 3,943,395, there is described a lamp including a tubular glass envelope having opposed press-sealed end portions, each of which contain the respective lead-in conductors which, when connected to the photocopier's power source (i.e., 110 VAC), provides electrical energy to the lamp's filament to cause activation thereof. As shown in this patent, lamps of this variety typically include an end cap of ceramic or the like material located on each of the press-sealed ends. These end caps are inserted within the corresponding connectors within the photocopier and connection is made at each end. One particular problem in such an arrangement is that many photocopier machines provide little accessibility at one of these connector locations, in effect, creating a "blind side". Providing positive electrical connection at these locations has thus proven somewhat difficult.
In the aforementioned Application Ser. No. 575,965, there is defined a lamp which overcomes this problem. It has been determined, however, that a lamp according to the design taught in Ser. No. 575,965 is operable only at wattage levels less than one hundred watts per inch. At wattages above this level, excessive heating of the contained inner lead and glass tubing member in which this lead is oriented has occurred. Such heating has in turn caused the tubing member to disfigure (i.e., melt), which in turn can cause the lamp to become inoperative. Accordingly, in Ser. No. 691,695, a lamp was defined wherein the inner lead and glass tubing member were located externally of the coiled filament supports, thus assuring a minimum spacing between the filament and these elements. Excessive heating was substantially prevented. In accordance with the teachings of the instant invention, a means is provided for preventing such excessive heating (and accompanying bowing of the tubing and inner lead) without the requirement of external placement as described in Ser. No. 691,695. It is understood, however, that the teachings of this invention are also applicable to and can be successfully utilized in the lamp defined in Ser. No. 691,695.
It is believed, therefore, that an improved tubular incandescent lamp of the type described in Ser. No. 575,965 wherein all electrical connections necessary to accomplish activation of the lamp are made at only one end thereof and which enables operation of the lamp at wattage levels substantially above those in Ser. No. 575,965 would constitute a significant advancement in the art. As such, this lamp would only make it necessary to provide a suitable non-electrical connector or the like in this "blind side" region of the photocopier, whereupon mere insertion of such a lamp therein would be possible without requiring electrical connection thereat. Equally significant, such a lamp would be substantially more versatile than that defined in Ser. No. 575,965 because it could be utilized not only in those present applications using said lamp but also in those situations wherein substantially greater wattages (i.e., greater than two hundred watts per linear inch) are demanded without possibly adversely affecting the operation of the lamp. The instant invention is particularly adaptable for use in such applications without the requirement for extensive modification to the photocopier machine.